Production of polyol polyesters having reduced color content

Abstract

Polyol polyesters having reduced color content are prepared by base-catalyzed transesterification of pretreated lower (i.e., C1-C3) alkyl fatty esters with polyols. The pretreatment comprises the steps of contacting the alkyl fatty esters (in a liquid state) with an alkoxide base, separating undissolved solids from the esters, and then distilling the esters.

What is claimed is: 
     
       1. A process for treatment of C 1  -C 3  alkyl esters of C 6  -C 22  fatty acids wherein at least 0.1% by weight of the fatty acid moieties contain conjugated or conjugatable sites of unsaturation, said process comprising the steps of: (A) contacting said C 1  -C 3  alkyl esters of fatty acids in a liquid state with an alkoxide base at a temperature of from about 60° C. to about 140° C. for from about 10 minutes to about 120 minutes, the said alkoxide base having the formula (RO) n  M, wherein R is an alkyl radical of from 1 to about 5 carbon atoms, M is an alkali metal, an alkaline earth metal or aluminum, and n is 1 when M is alkali metal, 2 when M is alkaline earth metal, and 3 when M is aluminum, and wherein the weight ratio of alkoxide base to ester is at least 0.005:1;   (B) separating undissolved solids from the liquid esters of Step A; and   (C) distilling the liquid esters from Step B and collecting the distilled esters.   
     
     
       2. The process of claim 1 wherein at least 0.5% by weight of the fatty acid moieties of the esters contain conjugated or conjugatable sites of unsaturation. 
     
     
       3. The process of claim 2 wherein M in the alkoxide is an alkali metal. 
     
     
       4. The process of claim 3 wherein in Step (B), the separation is done by centrifugation. 
     
     
       5. The process of claims 1, 2, 3 or 4 wherein the esters are methyl esters. 
     
     
       6. A process for preparing polyol polyesters of improved color from polyols and C 1  -C 3  alkyl esters of C 6  -C 22  fatty acids in which at least 0.1% by weight of the fatty acid moieties in said C 1  -C 3  alkyl fatty esters contain conjugated or conjugatable sites of unsaturation, the said process comprising: I. Pretreating said C 1  -C 3  alkyl fatty esters by a process comprising the steps of: (A) contacting said C 1  -C 3  alkyl fatty esters in a liquid state with an alkoxide base at a temperature of from about 60° C. to about 140° C. for from about 10 minutes to about 120 minutes, the said alkoxide base having the formula (RO) n  M, wherein R is an alkyl radical of from 1 to about 5 carbon atoms, M is an alkali metal, an alkaline earth metal or aluminum, and n is 1 when M is alkali metal, 2 when M is alkaline earth metal, and 3 when M is aluminum, and wherein the weight ratio of alkoxide base to ester is at least 0.005:1;   (B) separating undissolved solids from the liquid C 1  -C 3  alkyl fatty esters of Step A;   (C) distilling the liquid C 1  -C 3  alkyl fatty esters from Step B and collecting the distilled esters; and     II. Reacting the distilled C 1  -C 3  alkyl fatty esters from I(C) with a polyol in the presence of a basic catalyst and concurrently removing from the reaction mix the C 1  -C 3  alcohol formed during the reaction.   
     
     
       7. The process of claim 6 wherein at least 0.5% by weight of the fatty acid moieties of the C 1  -C 3  alkyl fatty esters contain conjugated or conjugatable sites of unsaturation. 
     
     
       8. The process of claim 7 wherein the alkyl fatty esters are methyl esters. 
     
     
       9. The process of claim 8 wherein the M in the alkoxide base is an alkali metal. 
     
     
       10. The process of claims 7, 8 or 9 wherein in Step II the polyol is selected from the group consisting of monosaccharides, disaccharides and sugar alcohols. 
     
     
       11. The process of claim 10 wherein Step II is carried out by a process comprising the steps of: i. forming a molten mixture of the C 1  -C 3  alkyl fatty ester, an alkali metal fatty acid soap and a basic catalyst selected from sodium carbonate, potassium carbonate, barium carbonate, and mixtures thereof, said molten mixture containing from about 10% to about 50% polyol, from about 40% to about 80% C 1  -C 3  alkyl fatty ester, from about 1% to about 30% of the soap and from about 0.05% to about 5% of the basic catalyst;   ii. adding excess C 1  -C 3  alkyl fatty ester to the melt of (i), the amount of C 1  -C 3  alkyl fatty ester being sufficient to raise the overall ester:polyol mole ratio above about 8:1;   iii. reacting the mixture from (ii) at about 120° C. to about 160° C. and a pressure of 0.1 to about 10 mm Hg for from about 2 to about 8 hours; and   iv. separating the polyol polyester from the reaction mix.